JP4018420B2 - Antifogging antireflection film, optical member using the same, and method of forming antifogging antireflection film - Google Patents

Description

【００３２】
【表２】

【００３３】
この実験結果から、本実施例のものが防曇効果を極めて長く維持することができるものであることが明らかである。
なお、上記経過日数に対するＮＧ発生率の関係をグラフに表したものを図３に示す。
【００３４】
【発明の効果】
以上に説明したように、本発明の防曇性反射防止膜およびこれを用いた光学部材ならびに防曇性反射防止膜形成方法によれば、ベーキングによる加熱処理を施したＭｇＦ_２層からなる防曇性被膜を反射防止膜の最上層に形成することにより、その防曇効果を長時間に亘って持続させることができる。
これにより、この防曇性反射防止膜が形成された光学部材においては、曇り現象により、その使用を中断しなければならないという不都合を減少させることができる。
【図面の簡単な説明】
【図１】本実施形態に係る防曇性反射防止膜を示す概略図
【図２】本実施形態に係る防曇性反射防止膜を形成した対物レンズをレンズ鏡胴に組み込んだ様子を示す概略図
【図３】本実施例と各比較例の評価結果を示すグラフ
【符号の説明】
１ ガラス基板
２ Ａｌ_２Ｏ_３層
３ ＺｒＯ_２層
４ ＭｇＦ_２層
５ 反射防止膜
６ コバ部
１０ 対物レンズ
１１、１２、１３ 光学部材
２０ レンズ鏡胴
３０ 密閉空間[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an antifogging antireflection film having an antifogging function, an optical member using the antifogging antireflection film, and a method for forming an antifogging antireflection film, and more specifically, functions as a partition at an end of a sealed lens barrel. The present invention relates to an antifogging antireflection film capable of enhancing the antifogging function of an antireflection film formed on an optical member such as an objective lens, an optical member, and a method for forming the film.
[0002]
[Background Art and Problems to be Solved by the Invention]
In a lens barrel etc. in which the inside is a sealed space, an objective lens functioning as a partition wall located outside the lens barrel is disposed, and an antireflection film is formed on the inner lens surface. Are known.
[0003]
By the way, it is well known that such an objective lens is easily affected by the external environment, and the lens surface inside thereof is clouded with a rapid temperature change in the external atmosphere. This fogging of the lens occurs when the surface temperature of the lens substrate falls below the dew point, and the water inside the sealed space becomes minute water droplets that adhere to the inner surface of the objective lens and scatter light.
Anti-fogging measures in this field are important because this fogging causes a visual field defect of the optical system and makes its use difficult.
[0004]
Conventionally, as an anti-fogging measure in such a field, in the process of incorporating the lens into the lens barrel, the working environment is low temperature and low humidity (25 ° C.
Although it is known that the temperature is kept at 30% RH or less), the effect has not been satisfactory.
[0005]
Thus, in recent years, for example, as disclosed in JP-A-2001-356201, a method of providing a hydrophilic film on the surface of an antireflection film is known. Shows very good antifogging properties, but the antifogging properties deteriorate rapidly with the passage of time. This is because a sufficient antifogging effect can be obtained if the contact angle of the hydrophilic film is 5 degrees or less (super hydrophilicity), but the contact angle of a general hydrophilic film is 10 to 20 degrees. If water droplets adhere to the surface of the surface, they gather close together to form very large water droplets and spread over a large area, which adversely affects optical performance more than normal cloudiness. It becomes.
[0006]
The present invention has been made in view of such circumstances, and an antireflection film is formed on the optical surface on the sealed space side of an optical member functioning as a partition between the sealed space and the outside. An object of the present invention is to provide an antifogging antireflection film capable of enhancing the persistence of the antifogging effect of the antireflection film, an optical member using the antifogging antireflection film, and a method for forming an antifogging antireflection film.
[0007]
[Means for Solving the Problems]
The antifogging antireflection film of the present invention is characterized in that an antifogging film made of MgF ₂ subjected to a baking treatment is provided on the uppermost layer.
[0008]
Further, the optical member of the present invention functions as a partition wall that is located at the end of the lens barrel and has a sealed space inside the lens barrel, and the antifogging antireflection film is formed on the optical surface on the lens barrel side. It is characterized by.
[0009]
The lens barrel is particularly effective when it is a lens barrel that houses a photographing optical system of the image pickup apparatus.
[0010]
In addition, the antifogging antireflection film forming method of the present invention comprises forming an antireflection film which is laminated on an optical substrate and having an MgF ₂ coating on the uppermost layer, and thereafter performing a baking treatment at a temperature of 150 ° C. or higher. The water content is removed.
[0011]
In this case, it is preferable that the baking process is performed before the optical member on which the antireflection film is formed is incorporated in the lens barrel.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 shows a state where an antifogging antireflection film of the present invention is formed on a lens substrate.
[0013]
That is, an Al ₂ O ₃ layer 2 and a ZrO ₂ layer 3 are sequentially formed on a glass substrate 1 as a lens substrate, and an MgF ₂ layer 4 is formed as the uppermost layer. The thickness of the MgF ₂ layer 4 is, for example, 100 nm.
The three layers 2, 3, and 4 constitute the antireflection film 5 as a whole, and are formed by a vacuum deposition method, a sputtering method, or the like.
[0014]
In addition, after the film formation, the glass substrate 1 and the reflective film 5 were heat-treated by baking at 200 ° C. The heating time is a time for sufficiently removing the water contained in the glass substrate 1 and the antireflection film 5, and depends on the size of the glass substrate 1, for example, in the case of a small lens, about 1 to 2 hours. Is enough.
[0015]
FIG. 2 shows a state in which the objective lens 10 on which the above-described antifogging antireflection film 5 is formed is incorporated in a lens barrel 20 used in an imaging apparatus such as a television lens. That is, as described above, the objective lens 10 is formed with the antireflection film 5 and subjected to a heat treatment by baking, and then the lens barrel 20 together with other optical members (lenses, filters, etc.) 11, 12, 13. Embedded in. In this assembly process, the temperature and humidity are maintained in an atmosphere of 25 ° C. and 30% or less, respectively.
[0016]
As shown in FIG. 2, the objective lens 10 functions as a partition wall with the outside at the end of the lens barrel 20, and forms a narrow sealed space 30 between the lens (optical member) 11. The antifogging antireflection film 5 described above is an abbreviation on a lens surface (hereinafter referred to as an inner lens surface) located on the sealed space 30 side when the objective lens 10 is incorporated in the lens barrel 20. It is formed on the entire surface. An edge portion 6 is formed in the outer peripheral area of the inner lens surface of the objective lens 10, and the edge portion 6 is subjected to a sanitizing process.
[0017]
By the way, such an internal sealed space 30 and each member around it (objective lens 10, lens (optical member) 11, lens barrel 20 and the like) are difficult to completely remove moisture, and also have sufficient moisture. Even if it is removed, as time passes, moisture penetrates into the internal sealed space 30 through each of the above members.
In particular, when the lens surface (hereinafter referred to as the outer lens surface) in contact with the outside of the objective lens 10 is exposed to cold air or is subjected to cold water and the surface temperature is lowered, the inner lens of the objective lens 10 is used. The surface temperature decreases, the dew point at this portion decreases, and fine water droplets adhere to the inner lens surface.
[0018]
Since the water droplets scatter light, the inner lens surface of the objective lens 10 becomes clouded over time. Such a fogging phenomenon is remarkable when the objective lens 10 is thin.
[0019]
Conventionally, a technique for improving the anti-fogging property by applying a hydrophilic coating to the inner lens surface is known. However, in the case of a hydrophilic coating, it is sufficient if the contact angle of the hydrophilic coating is 5 degrees or less (superhydrophilic). Although the antifogging effect is obtained, the contact angle of a general hydrophilic coating is 10 to 20 degrees, and once water droplets are formed on the inner lens surface, each particle gathers into large water droplets, In addition, since there is a tendency to spread on the inner lens surface, there is a possibility of causing a worse visibility than mere fogging.
[0020]
Based on such knowledge, the inventor forms an MgF ₂ layer 4 that functions as an antifogging film on the uppermost layer of the antireflection film 5 by changing the way of thinking. Further, the MgF ₂ layer 4 is baked by baking. The present inventors have found a technique for maintaining the antifogging effect of the antireflection film 5 by performing heat treatment.
[0021]
Although the mechanism for maintaining this anti-fogging effect has not been elucidated, the MgF ₂ layer 4 that has been baked at a predetermined temperature for a predetermined time and has sufficiently removed moisture from the interface with the air layer is formed into spherical particles. This is considered to be because the occurrence of the clouding phenomenon is delayed because it is separated from the surface of the inner lens surface, and at least the state in which these minute water droplets gather together can be avoided.
[0022]
Hereinafter, the effect of the present invention will be clarified by comparing the examples of the present invention with various comparative examples.
The layer structure of the antireflection film 5 is not limited to the above-described embodiments, aspects of the various configurations if it is possible to form a MgF ₂ layer 4 on the top layer are possible, the MgF ₂ layer 4 A single layer is also possible.
[0023]
【Example】
(Example): AR (antireflection film; the same applies to the following) + baked objective lens (glass substrate), Al ₂ O ₃ and ZrO ₂ layers are laminated, and MgF ₂ layer is further laminated on top to prevent reflection. A membrane was created. The contact angle of water droplets on the MgF ₂ layer in the initial state of film formation was 5 degrees or less.
[0024]
The objective lens on which the antireflection film was formed was baked at a heating temperature of 200 ° C. for 1 hour. This treatment sufficiently removed water in the objective lens substrate and the antireflection film. Thereafter, the objective lens was assembled in a lens barrel in a sufficiently dry atmosphere (temperature 25 ° C., humidity 30% or less) and sealed. The assembly was left in an atmosphere at a temperature of 40 ° C. and a humidity of 90%. The left assembly was once heat-treated at 60 ° C., and 5 ° C. cold water was applied to the outer surface of the objective lens subjected to the heat treatment. The relationship between the number of days elapsed and the ratio of the objective lens that had become cloudy was examined. In addition, it was set as the NG product when cloudiness occurred in part.
[0025]
(Comparative example 1): AR only As in the example, each layer of Al ₂ O ₃ and ZrO ₂ is laminated on the objective lens (glass substrate), and an MgF ₂ layer is further laminated on the uppermost part to create an antireflection film. did.
[0026]
The objective lens was assembled in a lens barrel in a sufficiently dry atmosphere (temperature 25 ° C., humidity 30% or less) and sealed without performing any baking treatment. The assembly was left in an atmosphere at a temperature of 40 ° C. and a humidity of 90%. The left assembly was once heat-treated at 60 ° C., and 5 ° C. cold water was applied to the outer surface of the objective lens subjected to the heat treatment. The relationship between the number of days elapsed and the ratio of the objective lens that had become cloudy was examined. In addition, it was set as the NG product when cloudiness occurred in part.
[0027]
(Comparative Example 2): Hydrophilic AR
Each layer of Al ₂ O ₃ and ZrO ₂ was laminated on the objective lens (glass substrate), and a hydrophilic SiO ₂ layer was further laminated on the uppermost part to prepare an antireflection film. The contact angle of water droplets on the SiO ₂ layer in the initial state of film formation was 5 degrees or less.
[0028]
Thereafter, the objective lens was assembled in a lens barrel in a sufficiently dry atmosphere (temperature 25 ° C., humidity 30% or less) and sealed. The assembly was left in an atmosphere at a temperature of 40 ° C. and a humidity of 90%. The left assembly was once heat-treated at 60 ° C., and 5 ° C. cold water was applied to the outer surface of the objective lens subjected to the heat treatment. The relationship between the number of days elapsed and the ratio of the objective lens that had become cloudy was examined. In addition, it was set as the NG product when cloudiness occurred in part.
[0029]
(Comparative Example 3): Each layer of Al ₂ O ₃ , ZrO ₂ , and MgF ₂ is laminated on an AR + water-repellent treatment objective lens (glass substrate), and a fluorine-based water-repellent coating is further laminated on the uppermost layer, and an antireflection film. Formed.
Thereafter, the objective lens was assembled in a lens barrel in a sufficiently dry atmosphere (temperature 25 ° C., humidity 30% or less) and sealed. The assembly was left in an atmosphere at a temperature of 40 ° C. and a humidity of 90%. The left assembly was once heat-treated at 60 ° C., and 5 ° C. cold water was applied to the outer surface of the objective lens subjected to the heat treatment. The relationship between the number of days elapsed and the ratio of the objective lens that had become cloudy was examined. In addition, it was set as the NG product when cloudiness occurred in part.
[0030]
(Evaluation)
As shown in Table 1 and Table 2 (indicating the number of days until the NG product reaches 100%), in Comparative Example 2, the total number became NG product when 2 days passed, and in Comparative Example 3, 4 days passed. At the time, all the products became NG products, and in Comparative Example 1, all the products became NG products after 7 days. In the comparative example, 40% of the comparative example 1 having the highest anti-fogging effect persistence was NG after 2 days.
On the other hand, in the present example, even when 18 days passed, the total number did not become NG products (NG generation rate 86%), and the generation rate of NG products exceeded 40% after 10 days. It was time.
[0031]
[Table 1]

[0032]
[Table 2]

[0033]
From this experimental result, it is clear that the present example can maintain the antifogging effect for a very long time.
In addition, what represented the relationship of the NG incidence with respect to the said elapsed days in the graph is shown in FIG.
[0034]
【The invention's effect】
As described above, according to the antifogging antireflection film of the present invention, the optical member using the antifogging antireflection film, and the antifogging antireflection film forming method, the antifogging comprising the MgF ₂ layer subjected to the heat treatment by baking is performed. By forming the protective film on the uppermost layer of the antireflection film, the antifogging effect can be maintained for a long time.
Thereby, in the optical member in which this anti-fogging anti-reflective film was formed, the inconvenience that the use must be interrupted by the fogging phenomenon can be reduced.
[Brief description of the drawings]
FIG. 1 is a schematic view showing an antifogging antireflection film according to the present embodiment. FIG. 2 is a schematic view showing a state in which an objective lens formed with the antifogging antireflection film according to the present embodiment is incorporated in a lens barrel. FIG. 3 is a graph showing the evaluation results of this example and each comparative example.
1 glass substrate 2 _Al 2 _{O 3} layer 3 ZrO ₂ layer 4 MgF ₂ layer 5 antireflection film 6 flange portion 10 objective lens 11, 12, 13 optical member 20 the lens barrel 30 enclosed space

Claims (5)

An antifogging antireflection film comprising an antifogging film made of MgF ₂ subjected to a baking treatment as an uppermost layer. The antifogging antireflection film according to claim 1 is formed on the optical surface of the sealed space, and functions as a partition wall that is located at an end of the lens barrel and serves as a sealed space inside the lens barrel. Optical member to be used. The optical member according to claim 2, wherein the lens barrel is a lens barrel that houses a photographing optical system of an image pickup apparatus. An anti-fogging anti-reflective film characterized in that it is laminated on an optical substrate and an anti-reflective film having an MgF ₂ coating is formed on the uppermost layer, followed by baking at a temperature of 150 ° C. or higher to remove moisture Film forming method. 5. The antifogging antireflection film forming method according to claim 4, wherein the baking is performed before the optical member on which the antireflection film is formed is incorporated in a lens barrel.

Images